A lidar (light detection and ranging) is a radar system which emits laser beams to measure characteristic quantities such as position and velocity of a target. According to the working principle of the lidar, first, a detecting laser beam is emitted to the target; next, a received signal reflected back from the target is compared with the emitted signal and is appropriately processed, then information about the target can be acquired, for example, parameters such as distance, position, altitude, velocity, posture and even shape of the target.
A multi-line lidar is a type of lidar which emits laser through a semiconductor laser emitter and detects reflected optical signals. A multi-line lidar comprises a plurality of laser emitters each can measure a distance. Emitting circuit devices of laser emitters are complex and large in size, and cannot be stacked in a sufficiently large number in a small space. The number of laser beams, namely the number of stacked laser emitters per unit area, is a key factor affecting the vertical resolution of a multi-line lidar. Consequently, prior art multi-line lidars remain to be improved in their vertical resolution.